Related papers: The Accretion Ejection Instability : Observationna…
We study a sample of 44 low-luminosity radio-loud AGN, which represent a range of nuclear radio-power spanning 5 orders of magnitude, to unveil the accretion mechanism in these galaxies. We estimate the accretion rate of gas associated with…
After an X-ray binary experiences a transient jet ejection, it undergoes a phase in which its X-ray light curve is dominated, for some time, by thermal emission from an accretion disk surrounding the black hole. The accretion physics in the…
A central compact object (CCO, e.g. a black hole) with an accretion disk has been suggested as the common central engine of various astrophysical phenomena, such as gamma-ray bursts (GRBs), tidal disruption events (TDEs) and active galactic…
We proposed that the spectral evolution of transient X-ray binaries (XrB) is due to an interplay between two flows: a standard accretion disk (SAD) in the outer parts and a jet-emitting disk (JED) in the inner parts. We showed in previous…
An instability can potentially operate in highly irradiated disks where the disk sharply transitions from being radially transparent to opaque (the 'transition region'). Such conditions may exist at the inner edges of transitional disks…
The X-ray light-curves of the recurring outbursts observed in low-mass X-ray binaries provide strong test beds for constraining (still) poorly understood disc-accretion processes. These light-curves act as a powerful diagnostic to probe the…
In accretion disks with large-scale ordered magnetic fields, the magnetorotational instability (MRI) is marginally suppressed, so other processes may drive angular momentum transport leading to accretion. Accretion could then be driven by…
The origin of turbulence in accretion discs is still not fully understood. While the magneto-rotational instability is considered to operate in sufficiently ionized discs, its role in the poorly ionized protoplanetary disc is questionable.…
Compact binaries have long been a paradigm for accretion theory. Much of our present view of how accretion occurs comes directly from the comparison of theory with observations of these sources. Since theory differs little for other objects…
Quasi-periodic oscillations (QPOs) in the X-ray lightcurves of accreting neutron star and black hole binaries have been widely interpreted as being due to standing wave modes in accretion disks. These disks are thought to be highly…
Approximately 10-20% of Active Galactic Nuclei are known to eject powerful jets from the innermost regions. There is very little observational evidence if the jets are powered by spinning black holes and if the accretion disks extend to the…
Physical mechanism responsible for high viscosity in accretion disks is still under debate. Parameterization of the viscous stress as $\alpha P$ proved to be a successful representation of this mechanism in the outer parts of the disk,…
In young circumstellar disks, accretion--the inspiral of disk material onto the central star--is important for both the buildup of stellar masses and the outcome of planet formation. Although the existence of accretion is well documented,…
LSI+61303 is one of the most observed Be/X-ray binary systems because, peculiarly, it has periodical radio and X-ray emission together with strong, variable gamma-ray emission. This source remains, however, quite enigmatic. Some properties…
We compiled the X-ray and soft gamma-ray observations of the Galactic black hole binary XTE J1859+226 in the 1999--2000 outburst from RXTE, ASCA, BeppoSAX and CGRO. Throughout systematic spectral analysis using a two-component model…
One of the principal scientific objectives of the upcoming Constellation-X mission is to attempt to map the inner regions of accretion disks around black holes in Seyfert galaxies by reverberation mapping of the Fe K fluorescence line. This…
The inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric…
We present a new picture for the central regions of Black Hole X-ray Binaries. In our view, these central regions have a multi-flow configuration which consists in (1) an outer standard accretion disc down to a transition radius r_J, (2) an…
Relativistically blurred reflection from the accretion disc provides a powerful probe of the extreme environments close to supermassive black holes; the inner regions of the accretion flow and the corona that produces the intense X-ray…
Context: Some apparently quiescent supermassive black holes (BHs) at centers of galaxies show quasi-periodic eruptions (QPEs) in the X-ray band, the nature of which is still unknown. A possible origin for the eruptions is an accretion disk,…